Fuel injection pump for internal combustion engines

ABSTRACT

A fuel injection pump is proposed, which has a centrifugal governor disposed in the suction chamber of the fuel injection pump, the governor having a sleeve displaceable on a piston, and a pressure chamber enclosed in the interior of the governor sleeve, the latter being defined by the end face of the piston. By means of a relief line of the pressure chamber which is opened in the offset position of the governor sleeve, the restoring force on the centrifugal governor is increased during starting by the amount of the pressure difference appearing at the governor sleeve. Beyond a predetermined adjustment of the governor sleeve, the relief line is blocked, so that the governor can function unhindered within the normal operational range. The hysteresis thus resulting upon the shut-off of the increased starting quantity improves the behavior of the engine as it runs up to operational speed.

BACKGROUND OF THE INVENTION

The invention is based on a fuel injection pump as revealed hereinafter.In an injection pump of this kind, such as that known from GermanOffenlegungsschrift No. 24 03 082.8, a starting lever is actuated by thegovernor sleeve and can be coupled via a starting spring with anadjusting lever, and the quantity adjusting member of the fuel injectionpump is articulated onto this starting lever. After the starting leverhas come to rest on the adjusting lever, the governor sleeve functionscounter to the force of an adjustable governor spring and controls thequantity of fuel to be injected, the quantity being effected via thefuel quantity adjusting member. The chamber enclosed between thegovernor sleeve and the piston communicates with the fuelfilled suctionchamber of the fuel injection pump, so that the governor sleeve iseasily displaceable.

In the known fuel injection pump, an increased starting quantity isestablished with this apparatus at the outset position of the governorsleeve. Depending on the design of the starting spring, this increasedstarting quantity is eliminated shortly before the idling rpm isattained, in that the governor sleeve causes the starting lever to cometo rest on the adjusting lever. However, in some engines, interruptionof the smooth, jerk-free operation of the engine occurs at thetransition from the starting enrichment to idling operation.

OBJECT AND SUMMARY OF THE INVENTION

The fuel injection pump has the advantage over the prior art that theelimination of the increased starting quantity does not take place at alower rpm than the idling rpm, but instead is effected only at a higherrpm. Thus the transition between the starting phase and idling operationcan be substantially improved. On the other hand, an increased fuelquantity, that is, the increased starting quantity, is prevented frombeing supplied to the engine when the rpm is dropping during idlingoperation. The reestablishment of the increased starting quantity iseffected according to the invention only when a relatively low rpm hasonce again been attained, so that over the entire load/rpm operation ofthe engine, an exessively increased fuel quantity is not injected.

Advantageous further embodiments and improvements to the apparatusdisclosed in the main claim are attainable by means of thecharacteristics disclosed in the dependent claims.

The invention wil be better understood and further objects andadvantages thereof will become more apparent from the ensuing detaileddescription of four preferred embodiments taken in conjunction with thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross sectional view of a fuel injection pump having acentrifugal governor, which acts upon a starting lever of a quantityadjusting device;

FIG. 2 shows a fragmentary first exemplary embodiment of the governor,embodied according to the invention, of a fuel injection pump in itsoutset position;

FIG. 3 shows another fragmentary view of the exemplary embodiment ofFIG. 2 having a governor sleeve in the operating position;

FIG. 4 shows another fragmentary view of a modified form of embodimentof the exemplary embodiment according to FIG. 2;

FIG. 5 shows another fragmentary view of a third form of embodiment ofthe governor embodied according to the invention; and

FIG. 6 shows still another fragmentary view of a fourth form ofembodiment of the governor embodied according to the invention, havingan additional discharge control location on the governor sleeve forinfluencing the pressure in the suction chamber of the fuel injectionpump.

DESCRIPTION OF A PREFERRED EMBODIMENT

A pump piston 3 simultaneously reciprocates and rotates within acylinder 2 of a housing 1 of a fuel injection pump. The pump workchamber 4 of this pump is supplied with fuel from a suction chamber 7via longitudinal grooves 5 disposed in the jacket face of the pumppiston and via a conduit 6 extending within the housing 1, as long asthe pump piston is executing its intake stroke or has assumed its bottomdead center position. As soon as the conduit 6 is closed upon thebeginning of the compression stroke and following a correspondingrotation by the pump piston, the fuel located in the pump work chamber 4is pumped into a longitudinal conduit 8 extending in the pump piston.From the longitudinal conduit 8, the fuel is carried further via abranching radial bore 9 and a distributor groove 10 disposed in thesurface of the pump piston to one of pressure lines 11 which areappropriately distributed about the circumference of the cylinder bore 2and which correspond in number to the number of engine cylinders to besupplied with fuel; these pressure lines 11 lead to the injection valves(not shown) of the individual cylinders of the engine.

The suction chamber 7 is supplied with fuel via a supply pump 13 from afuel supply container 14. The pressure in the suction chamber iscontrolled in accordance with rpm in a known manner by means of apressure control valve 15 parallel to the fuel supply pump 13.

Acting as the quantity adjusting member, an annular slide 16 isdisplaceable on the pump piston 3 and opens a radial bore 17communicating with the longitudinal conduit 8 during the course of thecompression stroke of the pump piston 3, thus determining the end offuel supply or determining the quantity of fuel supplied by the pumppiston to the pressure lines 11. The fuel flowing out after this radialbore 17 has been opened flows back into the suction chamber 7.

The annular slide element 16 is displaced via a starting lever 18, whichis pivotable about a shaft 19 inserted firmly into the housing and iscoupled at one end with the annular slide element 16. An rpm governorembodied as a centrifugal governor 23 and disposed in the suctionchamber engages the other arm of the intermediate lever 18. Thecentrifugal governor 23, which is driven by a gear mechanism (not shown)in accordance with the pump piston rpm, has a rotating carrier 24 onwhich flyweights 25 are disposed. Coaxially with the axis of the carrier24, the carrier has a piston 26, on which a sleeve 27 is disposed suchthat it is tightly displaceable. The sleeve 27 is closed at one end, andin its inner bore 29, together with the end face 31 of the piston, itencloses a pressure chamber 32. The lowermost end of the sleeve 27 isengaged by nose-like parts 28 of the flyweights 25, so that upon thedeflection of the flyweights 25, the sleeve is displaced by theflyweights axially on the piston 26, and itself simultaneously displacesthe starting lever 18 and the annular slide element 16.

A one-armed adjusting lever 30 is pivotably disposed on the same shaft19, independently of the starting lever 18. A governor springarrangement 33 is articulated to the end of this adjusting lever 30, andon the other end the governor spring arrangement 33 is suspended on anarbitrarily adjustable lever 37. An adjustable full-load stop 38 for theadjusting lever 30 is also provided.

A leaf spring 39 secured with its outer end to the adjusting lever 30protrudes into the interstice between the adjusting lever 30 and thestarting lever 18. The leaf spring is bent approximately at its middletoward the centrifugal adjuster 23 and rests on the starting lever 18.The leaf spring 39 tends to cause the two levers to spread apart.

The injection quantity regulation of the previously described injectionpump according to FIG. 1 functions as follows:

Depending upon the position of the annular slide element 16, the radialbore 17 and thus the relieving communication from the work chamber 4 tothe pump suction chamber 7 is opened earlier or later during thecompression stroke or supply stroke of the pump piston 3, and the fuelsupply into the pressure lines 11 is thus interrupted. In the topmostposition of the annular slide element 16, the maximum or the entire fuelquantity supplied by the pump piston 3 is thus delivered to the pressurelines 11. The farther the annular slide element 16 is displaced towardthe bottom, the earlier the radical bore 17 will be opened and theearlier supply will be interrupted. In the illustrated starting positionshown in FIG. 1, the adjusting lever 30 rests on the full-load stop 38,while the starting lever 18 is pressed by the leaf spring 39 against thesleeve 27 of the centrifugal adjuster 23. As a result of the deflectionof the starting lever 18, the annular slide element 16 is simultaneouslymoved into its uppermost position, corresponding to the supply of anexcess fuel quantity. After starting of the engine, the flyweights 25are deflected outward by the increasing rpm, so that the sleeve 27 isdisplaced upward, and with increasing rpm the sleeve 27 pivots thestarting lever 18 counter to the force of the leaf spring 39 until itcomes to rest on the adjusting lever 30. At this instant, the excessfuel quantity is reduced to the normal full-load quantity. As operationof the engine continues, with a further increase in rpm, the startinglever 18 together with the adjusting lever 30 is now pivoted, dependingupon the initial stressing of the governor spring arrangement 33, at thelatest upon the attainment of the breakaway rpm, and the annular slideelement 16 is thereby displaced still farther downward.

In the embodiment according to the invention, the governor sleeve 27 isguided tightly on the piston 26, is closed at one end and in its innerbore, together with the end face 31 of the piston 26, it encloses thepressure chamber 32 (FIG. 2). A connecting line 41 leads away from theend face 31, coaxially with the piston 26, and is embodied as a blindbore at the end of which a radial bore 42 leads away toward the jacketface of the sleeve. A throttle 43 is disposed in the radial bore 42. Inthe outset position shown in FIG. 2 for the governor sleeve 27, theradial bore 42 discharges into an annular groove 44, which is located onthe jacket face of the inner bore 29.

A relief line 46 which is embodied as a blind bore also extendscoaxially within the piston 26 and, as indicated in FIG. 1, leads to theintake side of the fuel supply pump 13 or to the fuel supply container14. At the end of the relief bore 46 in the piston 26, a radial bore 45branches off, likewise discharging into the annular groove 44 when thegovernor sleeve 27 is in the outset position. Means defining an opening48 is provided in the jacket portion of the governor sleeve 27 in orderto provide communication between the pressure chamber 32 and thesurrounding suction chamber; in the illustrated outset position of thegovernor sleeve 27, this opening 48 is closed by the piston 26, and upona displacement of the governor sleeve 27 after passing the end face 31,this means defining the opening 48 is consequently opened. From thispoint on, communication is established between the suction chamber 7 andthe pressure chamber 32.

The apparatus according to the invention functions as follows:

In the outset position of the governor sleeve 27, the communicationbetween the pressure chamber 32 and the suction chamber 7 isinterrupted, as has been noted. The pressure chamber 32 is, however,relieved toward the fuel supply container 14 via the connecting line 41,the radical bore 42, the annular groove 44, the radial bore 45 and therelief line 46. Upon starting of the engine, corresponding to the outsetposition of the governor sleeve 27 shown in FIG. 2, the annular slide 16assumes its uppermost position, so that the total quantity of fuelsupplied by the pump piston 3 reaches the injection locations. Withincreasing rpm, the pressure in the suction chamber 7 increases as well,yet the pressure in the pressure chamber 32 does not change. Thus as theengine runs up to operating speed, both the force with which thestarting spring presses onto the starting lever 18 and the differentialpressure between the pressure in the pressure chamber 32 and the suctionchamber 7 act upon the governor sleeve 27. The flyweights 25 mustaccordingly exert a force which has been increased by the product of thedifferential pressure and the surface area of the end face, in order tomove the governor sleeve 27 out of the outset position in order to shutoff the increased starting quantity. The shut-off of the increasedstarting quantity is thus effected at an rpm which is higher than thatin the case of the known art. Once the governor sleeve 27 has beendeflected to such an extent that the radial bore 45 is closed and theopening 48 has been opened by the end face 31 (FIG. 3), it is possiblefor a pressure equalization to take place in the pressure chamber 32, sothat the centrifugal governor functions in the conventional, knownmanner. The forces exerted by the fuel pressure onto the governor sleeve27 cancel one another out from this point on. As a result of theincreased restoring force exerted on the governor sleeve in the startingposition of the governor sleeve, the increased starting quantity is thusshut off only at a relatively high rpm, one which is already within theidling rpm range, while in contrast, when the rpm is dropping, the fullidling regulation path of the governor sleeve can be exploited withoutcausing the increased starting quantity to be supplied. Thus ahysteresis between the initiation and termination of the increasedstarting quantity is established. The full course of the hysteresis loopis only completed once the governor sleeve 27 has again assumed itsoutset position.

The hysteresis behavior can be influenced in terms of time by means ofthe throttle 43 provided in the radial bore 42.

For the embodiment according to FIG. 2, there is a long series ofequivalent solutions in terms of the functioning of such an apparatus.Naturally, the throttle 43 can be disposed in the radial bore 45 insteadof in the radial bore 42 (FIG. 6). FIG. 4 shows an embodiment in whichthe relief conduit 46 discharges via a radial bore 45' into an annulargroove 50 on the piston 26. The radical bore 45' may then be embodied asa throttle bore. In the illustrated outset position of the governorsleeve 27', the annular groove 50 communicates with an inner annulargroove 51 in the jacket face of the inner bore 29 of the governor sleeve27'. The inner annular groove 51 has a throttle connection to the pumpsuction chamber via an opening 52 in the jacket of the governor sleeve27'. The inner annular groove 51 furthermore communicates, in theillustrated outset position of the governor sleeve 27', with alongitudinal groove 53 which begins at the end face 31 of the piston26'.

In the exemplary embodiment according to FIG. 4, in the outset positionof the governor sleeve 27', the fuel flows out of the suction chamber 7via the opening 52, the inner annular groove 51, the annular groove 50,and the radial bore 45' to the relief line 46. The pressure chamber 32also communicates with the relief line 46 via the longitudinal groove53, so that the pressure in this pressure chamber 32 is reduced incomparison with that in the suction chamber 7. As soon as the rpm ishigh enough, that is, the centrifugal force acting upon the governorsleeve 27' is great enough, to overcome both the force of the startingspring and the force resulting from the differential pressure, theannular groove 50 is closed with the raising of the governor sleeve 27',and the pressure prevailing in the suction chamber 7 is delivered viathe longitudinal groove 53 to the pressure chamber 32. From thisbreakaway point on, the governor operates in a normal fashion as alreadydescribed for the foregoing exemplary embodiment.

The advantage in the embodiment according to FIG. 4 is that as a resultof the throttling effect of the opening 52 in combination with theradial bore 45', a desired pressure can be established in the pressurechamber 32, and thus the additional hydraulic force acting upon thegovernor sleeve 27', can be determined. The hysteresis behavior of thegovernor is thus established as well. An advantageous embodiment of FIG.4 provides that the relief bore is realized as a through longitudinalbore in the piston 26', and in order to close the relief bore 46, aclosure capsule 54 is pressed in from the direction of the end face 31.

A modification of the embodiment of FIG. 2 is shown in FIG. 5. Here, anannular groove 44' is provided on the piston 26", corresponding infunction to the annular groove 44 of FIG. 2. A longitudinal groove 41'is provided as a connecting conduit between the annular groove 44' andthe pressure chamber 32. This longitudinal groove 41' is located in thejacket face of the inner bore 29 of the governor sleeve 27". Thus, inthe outset position of the governor sleeve, the longitudinal groove 41'connects the annular groove 44' with the pressure chamber 32. The reliefconduit 46 of the embodiment of FIG. 2 is furthermore realized in FIG. 5in part by a longitudinal groove 56, which is likewise disposed in thejacket face of the inner bore 29 of the governor sleeve 27" and in theoutset position of the governor sleeve communicates with the annulargroove 44'. The longitudinal groove 56 is furthermore in continuouscommunication, that is, independently of the position of the governorsleeve, with a second annular groove 57 which is disposed in the jacketface of the piston 26" and communicates via a radial bore 58 with therelief line 46'. One of the longitudinal grooves 41' or 56 may therebybe embodied as throttle restrictions. The pressure chamber 32 can alsobe made to communicate via an opening 48 in the governor sleeve 27" withthe surrounding suction chamber 7. The opening 48 may either bedisposed, as in the exemplary embodiment of FIG. 2, such that in theoutset position of the governor sleeve 27" it is closed by the piston26', or else the pressure chamber 32 may communicate continuously withthe suction chamber 7 via an opening 48' disposed instead at a higherlevel. In this arrangement adapted to the embodiment of FIG. 4, theopening 48' must be embodied as a throttle opening, in order toestablish a desired pressure which has been decreased relative to thesuction chamber pressure.

In addition to these illustration embodiments, there are also furthervariant embodiments which need not be described in detail here. Theannular groove may be disposed either in the piston as shown or in theinner sleeve wall, and both lines and grooves may be used as connectingelements between the sleeve and pressure chamber on the one hand and thesleeve and the relief line on the other. On the other hand, alongitudinal groove can also be used instead of an annular groove, andthen corresponding annular grooves are provided in the sleeve and pistonin order to reliably assure the control functions of the connectionbetween the pressure chamber 32 and the relief line 46'. These annulargrooves can then communicate in turn, via longitudinal grooves or bores,with the pressure chamber or the relief line.

In another advantageous construction of FIG. 6 there is shown anembodiment in which the relief line 46 according to the embodiment ofFIG. 2, the relief line 46'" in FIG. 3, serves to receive fuel whichflows out of the suction chamber in a controlled manner in order toinfluence the pressure in the suction chamber. To this end, a radialthrough bore 60 is provided in a manner known per se in the piston 26'",intersecting the relief line 46'". In the area of the outlet of theradial throughbore 60, an annular groove 61 is provided on the piston26'", cooperating with openings 62 in the jacket of the governor sleeve27'". Beyond a specific deflected position of the governor sleeve, theopenings 62 come into communication with the annular groove 61, so thatfuel can now flow out of the suction chamber into the relief line 46'",and the pressure in the suction chamber is lowered. In order to improvethe transitional behavior, the annular groove 61 is embodied with adepth which decreases in the direction of the openings 62.

With this embodiment, an advantageous combination is attained,generating a starting hysteresis behavior on the part of the governorfor controlling the increased starting quantity and providingload-dependent control of the pressure in the suction chamber 7.

The foregoing relates to preferred exemplary embodiments of theinvention, it being understood that other embodiments and variantsthereof are possible within the spirit and scope of the invention, thelater being defined by the appended claims.

What is claimed and desired to be secured by Letters Patent of theUnited States is:
 1. A fuel injection pump for internal combustionengines having a fuel supply pump generating an rpm-dependent pressurein a suction chamber of the fuel injection pump and an rpm governorprovided with a governor sleeve, said sleeve being displaceable on apiston having end and jacket faces by means of an rpm-dependent forcecounter to the force of a governor spring arrangement which furthercomprises a starting spring, further wherein said governor sleeveactuates a fuel quantity adjusting device in such a manner that with anincreasingly long adjustment path of said governor sleeve the fuelquantity is reduced, said governor sleeve further arranged to enclose inits interior a pressure chamber defined by said end face of said pistonand said pressure chamber being connectable with said pump suctionchamber which surrounds said governor sleeve, characterized in that saidpressure chamber, in said governor sleeve has an outset position and atsaid outset position said pressure chamber communicates via a reliefline with a chamber of lower pressure, and further that said relief lineis closable beyond a predetermined stroke of said governor sleeve bymeans of a control edge.
 2. A fuel injection pump as defined by claim 1,characterized in that said relief line is disposed in said piston andarranged to discharge into a recess disposed in said governor sleeve,said recess further including a limitation edge adapted to communicatewith said pressure chamber, at least in the outset position of thegovernor sleeve, via a connecting line and further that saidcommunication between said relief line and said connecting line can beinterrupted by means of said axial limitation edge of said recess aftera predetermined stroke of said governor sleeve has been executed.
 3. Afuel injection pump as defined by claim 1, characterized in that saidsaid relief line is disposed in said governor sleeve and arranged todischarge into a recess disposed in said piston, said recess furtherincluding a limitation edge adapted to communicate with said pressurechamber, at least in the outset position of the governor sleeve, via aconnecting line and further that said communication between said reliefline and said connecting line can be interrupted by means of said axiallimitation edge of said recess after a predetermined stroke of saidgovernor sleeve has been executed.
 4. A fuel injection pump as definedby claim 2, characterized in that said relief line is disposed in theinterior of said piston and further includes a radial outlet at saidjacket face of said piston and further that said radial outlet, in theoutset position of the governor sleeve, discharges into a recess in saidjacket face of said governor sleeve and further that said recess has acontrol edge.
 5. A fuel injection pump as defined by claim 4,characterized in that said communication between said recess and saidpressure chamber can be established via a connecting line extendingwithin said piston and exiting in the vicinity of said recess.
 6. A fuelinjection pump as defined by claim 4, characterized in that saidconnection between said recess and said pressure chamber is embodied asa groove in said jacket face of said piston.
 7. A fuel injection pump asdefined by claim 4 or 5, characterized in that said recess is an annulargroove.
 8. A fuel injection pump as defined by claim 2 or 3,characterized in that said relief line further includes a throttle.
 9. Afuel injection pump as defined by claim 2 or 3 characterized in that athrottle is provided in said connecting line.
 10. A fuel injection pumpas defined by claim 7 or 8, characterized in that said connectionbetween said pressure chamber and said pump suction chamber comprisesmeans defining an opening in said governor sleeve in proximity to saidcontrol edge.
 11. A fuel injection pump as defined by claim 10,characterized in that said means defining said opening comprises athrottle.
 12. A fuel injection pump as defined by claim 2 or 3,characterized in that said connection between said pressure chamber andsaid pump suction chamber is embodied as means defining an opening insaid governor sleeve, and in the outset position of said governor sleevesaid opening is closed by said piston.
 13. A fuel injection pump asdefined by claim 4, characterized in that said relief line comprises anaxial bore beginning at the end face of the piston, the connection ofthis axial bore with the pressure chamber being closed by a closurepiece, and this axial bore having a radial bore on the relief side ofthe closure piece.